1. Field of the Invention
The present invention relates to an electroconductive polymer composition, an electroconductive polymer material and a method for producing the electroconductive polymer material.
2. Description of the Related Art
In recent years, an image display unit (display) typified by liquid crystal display (LCD), plasma display panel (PDP) and electroluminescence (EL) devices or the like has been widely used in various fields such as television sets, computer and various types of mobile instruments which have recently been spreading increasingly, and are undergoing remarkable development. On the other hand, solar batteries are attracting attention as one of non-fossil energies which pay consideration to global environment. In order to address the need for further spread of solar batteries, research for improving the functions thereof and the like has been demanded. An electroconductive film has been used for such display element and solar battery.
Generally, electroconductive films using a metallic material, such as ITO-based electroconductive films, are produced by forming, on a glass substrate, a film from a metallic material by a vapor phase methods such as a vacuum deposition method or a sputtering method. Display devices such as portable telephone and mobile instruments have been becoming lighter in weight, and it has been demanded that display device substrate is shifted from glass to plastic. The introduction of a plastic substrate has reduced the weight of display devices to become a half or less in comparison to the convectional products, and a plastic substrate has been remarkably improved in strength and impact resistance.
There, however, is a problem with regard to ITO-based electroconductive films in that the substitution of glass substrate with plastic films results in a decrease in adhesiveness, and making a substrate and a formed electroconductive film prone to easily peel off each other. Moreover, metallic materials, such as ITO, are ordinarily formed into a film by using a vapor phase method such as sputtering, so that an expensive production apparatus needs to be used.
An electroconductive polymer is known as a conductive material instead of metallic materials such as ITO. The use of an electroconductive polymer allows a conductive thin film to be formed by coating and offers the advantage that a conductive thin film may be inexpensively produced. Moreover, an electrode made of an electroconductive polymer is more flexible and less brittle than ITO electrodes, and it therefore is less prone to break even though it is used for flexible items. Thus, it also has an advantage that the application of an electrode made of an electroconductive polymer to a touch screen requiring a particularly high flexible electrode allows the life span of the device to be prolonged.
As such an electroconductive polymer, polythiophene containing polyanion has been developed, and a technique for forming an electroconductive film by using this polymer is disclosed in the specification of European Patent No. 440957. It, however, has become clear that this electroconductive film is slightly weaker in durability than ITO films and the like and that it may not achieve a durability sufficient for practical use in some applications.
In particular, when the electroconductive film is applied to display devices, photo-durability, that is, that transparency and conductivity are not decreased even after being irradiated with light to some extent or more, is very important.
For such a problem, an electroconductive film such in which polyphosphoric acid and a specific phenolic compound are added to polythiophene has been proposed in Japanese Patent Application National Publication (Laid-Open) No. 2006-505099. According to this document, the addition of polyphosphoric acid or the like makes photo-durability improve, namely, the increase of surface is inhibited upon exposure to light.